1. Field of the Invention
The invention relates to an electric power steering device that assists vehicle steering operation.
2. Description of Related Art
Japanese Patent Application Publication No. 2008-137486 (JP 2008-137486 A) describes this kind of electric power steering device. The electric power steering device includes a torque sensor that detects a steering torque applied by a driver to a steering mechanism, and a control device that controls drive of a motor. The control device sets an assist command value based on the steering torque detected by the torque sensor and controls the drive of the motor to cause assist force from the motor to follow the assist command value.
While a vehicle is traveling, a reverse input associated with a road surface reaction force generated depending on a road condition is transmitted from steered wheels of the vehicle to a steering wheel through a steering mechanism. A driver can then obtain information such as a road condition and grip force of the steered wheels while driving the vehicle through the reverse input transmitted to the driver's hands grasping the steering wheel. The reverse input also includes braking vibrations or the like as well as road surface reaction force, which is a factor for poor steering feel. Accordingly, if a required reverse input only is can be transmitted more appropriately, the steering feel can be improved.